1. Field of the Invention
The production of oxirane compounds such as propylene oxide by the catalytic reaction of an olefin with an organic hydroperoxide is a process of great commercial importance. Generally a homogeneous molybdenum catalyst is employed. The Oxirane Process for the co-production of propylene oxide and styrene monomer is illustrative of this technology.
The process of the instant invention relates to the separation of molybdenum epoxidation catalyst values in such epoxidation process technology.
2. Description of Related Art
An extremely successful process for the co-production of propylene oxide and styrene monomer involves the molecular oxygen oxidation of ethyl benzene to form ethyl benzene hydroperoxide, the catalytic reaction of the hydroperoxide with propylene to form propylene oxide and 1-phenyl ethanol, and the dehydration of the 1-phenyl ethanol to styrene monomer. The basic patent describing this process is U.S. Pat. No. 3,351,635.
In practice of the process, the epoxidation reaction mixture, usually after separation of unreacted propylene by distillation, is treated with aqueous caustic in an amount in excess of that necessary both to react with contained molybdenum values to from sodium molybdate and to react with organic impurities such as acids and phenols which are also contained in the epoxidate. See U.S. Pat. Nos. 4,405,572, 5,276,235, and 5,171,868, for example.
A problem which has existed in such prior practices has been the formation of relatively large quantities of an aqueous process stream containing molybdenum, sodium and organics, and the disposal of such aqueous process streams. The presence of molybdenum is particularly troublesome since this material must be removed prior to outfall to satisfy environmental restrictions.